Non-contact methods of determining the position of an object based on generating a magnetic field and measuring its strength at the object are well known in the art. For example, U.S. Pat. No. 5,391,199, and PCT patent application publication WO 96/05768, which are incorporated herein by reference, describe such systems for determining the coordinates of a medical probe or catheter inside the body. These systems typically include one or more coils within the probe, generally adjacent to the distal end thereof, connected by wires to signal processing circuitry coupled to the proximal end of the probe.
U.S. Pat. No. 4,710,708, which is incorporated herein by reference, describes a location determining system using a single axis solenoid with a ferromagnetic core as a radiating coil. There are a plurality of magnetic coil receivers. The position of the solenoid is determined assuming that it radiates as a dipole.
PCT patent application publication WO 94/04938, which is incorporated herein by reference, describes a position-finding system using a single sensing coil and an array of three, three-coil radiators. The radiator coils are wound on non-ferromagnetic forms. The position of the sensing coil is determined based on a dipole approximation to the magnetic fields of the coils where an estimate of the orientation of the sensor coil is first utilized in order to determine the position of the sensor coil in that order. Additionally, the radiator coils of each array are energized sequentially using a time multiplexing approach. Interestingly, although this reference discloses that frequency multiplexing can be utilized in order to significantly increase the operating speed of the position system, it clearly indicates that there are disadvantages to this type of approach due to its complexity. It is also important to note that although this reference teaches a single axis sensor position and orientation tracking system, it does not address any specific method for calibrating the system.
Accordingly, to date, there is no known system or method that provides for a electromagnetic position sensor single axis system and method that is capable of being simultaneously driven through frequency multiplexing utilizing a novel exact solution technique and a novel calibration method.